Mouse models for cystic fibrosis require critical knowledge of the endogenous mouse CFTR gene. We propose to characterize the regulation of the mouse CHR gene by uncovering DNA sequence binding motifs that mediate the expression of the gene. We determined the DNA sequence of 1122 bp upstream of exon l and uncovered putative regulatory DNA stretches and similarities to the human regulatory CFTR region. Transfection of deletional constructs linked to a reporter gene (CAT) from this mouse region into mouse, rectum adenocarcinoma and fibroblast cell lines revealed positive and negative cis-acting elements. We would like to extend these studies to expose further upstream sequences and test their ability to induce expression of the reporter gene in both mouse and human cell lines. The specificity of these and novel regulatory sequences as, well as their tissue specific distribution will be assessed in transgenic mice harboring the reporter gene constructs. We will also derive primary cultures from different tissues that express CFTR in order to study thin vivo binding of regulatory proteins to the DNA sequence motifs uncovered by the transfection assays.